The effect of combined oral contraception on testosterone levels in healthy women: A systematic review and meta-analysis

Abstract

Background: Combined oral contraceptives (COCs) reduce levels of androgen, especially testosterone (T), by inhibiting ovarian and adrenal androgen synthesis and by increasing levels of sex hormone-binding globulin (SHBG). Although this suppressive effect has been investigated by numerous studies over many years, to our knowledge no systematic review concerning this issue had been performed. This systematic reviewand meta-analysis was performed to evaluate the effect of COCs on concentrations of total T, free T and SHBG in healthy women and to evaluate differences between the various types of COCs (e.g. estrogen dose, type of progestin) and the assays used to assess total T and free T. methods: Areview of the literature was performed using database searches (MEDLINE, EMBASE and the CochraneCentral Register of Clinical Trials) and all publications (from inception date until July 2012) investigating the effect of COCs on androgen levels in healthy women were considered eligible for selection. Three reviewers were involved in study selection, data extraction and critical appraisal. For the meta-analysis, data on total T, free T and SHBG were extracted and combined using random effects analysis. Additional subgroup analyses were performed to evaluate differences between the various types of COCs (e.g. estrogen dose, type of progestin) and the assays used to assess total T or free T. results: Atotal of 151 records were identified by systematic reviewand 42 studies with a total of 1495 healthy young women (age range: 18- 40 years)were included in the meta-analysis. All included studies were experimental studies and 21 were non-comparative. Pooling of the results derived from all the included papers showed that total T levels significantly decreased during COC use [mean difference (MD) (95% confidence interval, CI) -0.49 nmol/l (-0.55, -0.42); P <0.001]. Significantly lower levels of free T were also found [relative change (95% CI) 0.39 (0.35, 0.43); P , 0.001], with a mean decrease of 61%. On the contrary, SHBG concentrations significantly increased during all types of COC use [MD (95% CI) 99.08 nmol/l (86.43, 111.73); P < 0.001]. Subgroup analyses revealed that COCs containing 20-25 mg EE had similar effects on total and free Tcompared withCOCswith 30-35 μg EE. In addition, suppressive effects onT levels were not different when comparing different types of progestins. However, subgroup analyses for the estrogen dose and the progestin type in relation to changes in SHBG levels did showsignificant differences: COCs containing second generation progestins and/or the lower estrogen doses (20-25 μg EE) were found to have less impact on SHBG concentrations. conclusions: The current literature review and meta-analysis demonstrates thatCOCsdecrease circulating levels of total Tand free T and increase SBHG concentrations. Due to the SHB Gincrease, free T levels decrease twice asmuchas total T. The estrogen dose and progestin type of the CO Cdonot influence the decline of total and freeT, but both affect SHBG. The clinical implications of suppressed androgen levels duringCOC use remain to be elucidated. © The Author 2013. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology.